Radio frequency (RF) communication systems that make use of frequency division multiplexing (FDM) are known. In such systems, commonly known as trunked communication systems, communication channels are assigned for use from time to time to subscribers as needed. To facilitate the channel assignment mechanism, such systems generally provide either a dedicated control channel that supports the channel assignment signalling, or the control channel function is distributed amongst the voice channels; for example, by providing the control channel information subaudibly simultaneously with voice traffic.
RF systems that make use of time division multiplexing (TDM) are also known. In these systems, a communication frequency (or pair of frequencies) is divided by time into frames and slots, and subscribers are assigned a slot to support their communication needs.
Combined FDM/TDM systems are also known. In such systems, a subscriber will be assigned a particular time slot on a particular frequency (or pair of frequencies) to support its communication needs. These systems provide a control slot on one of the frequencies to support the channel assignment information.
The known FDM, TDM, and FDM/TDM communications systems do not economically support many desired features. For example, full duplex RF capabilities must be provided in an FDM radio to support full duplex communications. While a properly configured TDM or FDM/TDM radio can support full duplex communications without full duplex RF capabilities, channel access time, channel monitoring capabilities and other features in such systems are often degraded.
A need exists for a communication system that will economically support needed and desirable features and options while simultaneously offering high quality communications and operability.